1. Field of the Invention
The present invention relates to an organic light emitting device having a light resonator structure and a display unit using the organic light emitting device.
2. Description of the Related Art
In these years, as one of flat panel displays, an organic EL display that displays images by using the organic EL (Electro Luminescence) phenomenon has been noted. Since the organic EL display is a self-luminous type display that displays images by using the foregoing light emitting phenomenon, the organic EL display is superior in terms of the wide view angle, the small power consumption, and the light weight.
The organic EL device mounted on the organic EL display mainly has a structure in which an organic layer is provided between an anode and a cathode. The organic layer includes a light emitting layer as a light emitting source and a hole-transport layer, an electron transport layer and the like for emitting light from the light emitting layer.
Specially, in an active matrix drive system organic EL display unit, the top emission structure capable of maintaining a large aperture ratio of a pixel has been developed (for example, refer to Japanese Unexamined Patent Application Publication Nos. 2003-203781, 2003-203783, 2003-323987, 2004-146198, 2004-152542, 2005-032618, 2005-276542, and 2005-530320). Such a structure is a device structure having a light-reflective lower cathode and a light-transparent upper anode, and different from the structure having a light-transparent lower anode and a light-reflective upper cathode that has been developed in the past. The top emission structure is not affected by lowering of the aperture ratio due to a TFT (Thin Film Transistor) and wiring. Therefore, it is thought that the top emission structure can provide an organic EL display unit with high display performance and superior long-term reliability.
Further, in the top emission structure, as a technique to improve color purity of blue light, green light, and red light, the following technique has been known. In such a technique, in the device structure having a light-reflective lower anode and a light-semi-transparent upper cathode, light generated from the light emitting layer in the organic layer is reflected and resonated (for example, refer to International Publication No. WO 01/039554 and Japanese Unexamined Patent Application Publication No. 10-177896). The device structure of the organic EL device having the light resonant function is generally called “light resonator structure (so-called micro-cavity structure).” In particular, in the organic EL device having the light resonator structure, the light extraction efficiency is improved, that is, the front optical power is increased, and the color purity is improved. Therefore, the organic EL device having the light resonator structure is suitable for a full color display.